Spirometra mansonoides was discovered, described, named, and its life cycle worked out by the author in 1935. It was the first cestode to be grown in vitro (Mueller, 1959). In the course of this work it was found to produce a potent growth factor (SGF) which can replace pituitary growth hormone in the hypox rat. Current studies with Dr. Monroe S. Glitzer of Merck (Rahway, N.J.) involve growing the sparganum larva of the worm in massive quantities in order to isolate and characterize the growth factor. With Dr. T. Noguchi, of Tokyo, Japan, a study is being pursued on the effect of SGF on the development of the rat brain. I am providing quantities of spargana to Dr. Paul P. Weinstein, of Notre Dame University, in a collaborative study on the role of vitamin B12 in the physiology of the worm. Like its close relative, the fish tapeworm, D. latum, Spirometra takes up large quantities of vitamin B12 the purpose of which is not understood. A separate study, with Sharon Edwards, involves a scanning electron microscope study of the topography of the tegument of the worm, Spirometra mansonoides, and S. mansoni. I am also furnishing large quantities of material (eggs, larval stages, and adult worms) to Dr. David Beach and Dr. George Halz, of this institution, for a study of the spectrum of fatty acids in the worm and changes that occur from one stage to the next.